The outer portion of a human eye has several layers including the sclera, which is an outer layer, and the retina, which is a light-sensitive inner layer. The choroid is a layer between the sclera and the retina that includes blood vessels and connective tissue. The choroid includes an inner layer referred to as the Bruch's membrane that is adjacent an outer layer of the retina referred to as the retinal pigment epithelium (RPE). In some instances, Choroidal Neovascularization (CNV) occurs in which abnormal new blood cells grow in the choroid that penetrate the Bruch's membrane and extend through the RPE into the retina. CNV can cause vision loss and/or impairment and is involved in a number of retinal diseases such as, for example, age-related macular degeneration (AMD) and high myopia. Early detection and monitoring of CNV can be significantly helpful in controlling disease progression.
Conventional approaches for detecting CNV include, for example, fluorescein angiography (FA) and indocyanine green angiography (ICGA). Both FA and ICGA have drawbacks, however. Neither modality is depth resolved and thus determination of neovascularization caused by CNV is typically based on a clinician's judgment rather than quantitative results. Furthermore, both FA and ICGA require intravenous dye injection, which can result in nausea and other side effects, and may not be available for repeated use on patients. Optical coherence tomography (OCT) micro-angiography (OCTA) is another imaging modality that can be used to detect CNV. OCTA can have advantages over FA and ICGA (and other approaches) in that OCTA can provide localized depth information and can be performed without administering a contrast agent. In many OCTA images, however, a tailing effect from overlaying blood vessels can lead to strong image artifacts appearing in the results of blood vessel networks within the outer retinal space and choroid. These image artifacts can significantly hinder the ability to visualize and interpret 3D angiographic results, thereby reducing the effectiveness of OCTA as a tool for CNV diagnosis.